The invention relates to a sprinkler comprising a holder body, at least one nozzle, a heat-activated release means and a cover which in a protective position is arranged in front of said nozzle when the sprinkler is in an inactive mode, the sprinkler comprising means for providing a displacement of the cover from the protective position to a free position in which the cover keeps clear of the nozzle so that it can spray extinguishing medium when the sprinkler is in an active mode, the holder body comprising an inlet for incoming extinguishing medium.
Such sprinklers are known for example from U.S. Pat. Nos. 4,014,388 and 4,880,063. The cover serves to provide an aesthetically appealing sprinkler of a type which in an inactive mode is concealed in a ceiling, for example. In such concealed sprinklers the cover mainly serves to keep a deflect plate in a retracted position for aesthetic reasons.
In these known sprinklers, the cover falls downwards when the material holding the cover in position melts as it is exposed to heat. Once the cover falls, the heat-activated release means of the sprinkler immediately comes into contact with heat, releasing the sprinkler.
Thus these known sprinklers are characterized in that the nozzle or nozzles more or less immediately start to spray extinguishing medium when the cover is displaced.
In certain conditions/surroundings, the sprinklers are exposed to dirt, dust, deposits and other material that can disturb the sprinklers"" qualities of reacting to fire or even prevent the supply of extinguishing medium in a fire. Sprinklers are installed in order that they operate, when required, up to several years after installation and, consequently, they are naturally exposed to dirt in certain surroundings. A cover in the form of a plate (cf. U.S. Pat. Nos. 4,014,388 and 4,880,063, for example) installed in front of the nozzles mainly provides mechanical protection against impacts. Some protection against dirt may be provided, but these known sprinklers are mounted in surroundings where dirt presents no problem. In certain surroundings the amount of dirt and impurities is so high that no sprinklers at all have been mounted, the assumption being that they would not operate reliably. This is the case although sprinklers are most desirable in some of these applications. As examples may be mentioned open rail cars transporting expensive equipment that may catch fire, for example vehicles. Other applications include painters"" shops and steel plants.
Another major problem in fire extinguishing installations is the synchronization of fire detection with fire extinguishing in such a way that fire extinguishing takes place as rapidly as possible on the site of the fire, i.e. by means of the sprinklers that are located nearest to the fire.
Said problems exist for example in windy surroundings where the heat from the fire is conveyed to sprinklers which are not near the fire. Should these sprinklers have a release means which reacts rapidly to heat, they start to spray extinguishing medium at a location where there is no fire. For this reason in this kind of surroundings sprinklers are used that are released relatively slowly. However, the more slowly the sprinklers are released, the longer the fire has time to advance. Slow initialization of fire extinction is naturally to be avoided, if possible. For the above reasons, known sprinklers are unable to operate as well as is desirable in said surroundings.
Mechanical loads may also make a sprinkler release unnecessarily (especially if the release means of the installation fails). Such mechanical loads may be created by impacts caused by trucks, lorries etc. in industrial halls, garages and on car decks onboard ferries.
In some surroundings there is the risk of a fire starting by an explosion. In such surroundings the ampoule of the sprinkler is likely to be released by the pressure even though no fire or even a risk of fire exists near the sprinkler. Such surroundings include transformers, paint cabinets and paint stocks.
The object and idea of the invention is to provide a sprinkler which has a simple structure and an inactive mode in which the sprinkler is not activated or does not get released when directly exposed to heat from flue gases, but which in another functional mode, called standby mode, rapidly becomes released when being exposed to heat from flue gases. Accordingly, the sprinkler can shift from the inactive mode to a standby mode without being activated by heat from flue gases that are directed to the sprinkler. Typically, the structure of sprinklers is such that nozzles and other components are simultaneously protected against dirt, dust, deposits and other material that could disturb the sprinkler""s qualities of reacting to fire or delivering extinguishing medium. The sprinkler can advantageously be used in surroundings where the only function of the cover is to protect the ampoule against dirt, dust and/or deposits, i.e. in surroundings where the sprinkler""s quality of protecting the ampoule against heat is of no significance.
For the above purposes, the present invention provides a sprinkler comprising a holder body, at least one nozzle, a heat-activated release means and a cover which in a protective position is arranged in front of said nozzle when the sprinkler is in an inactive mode, the sprinkler comprising means for providing a displacement of the cover from the protective position to a free position in which the cover keeps clear of the nozzle so that it can spray extinguishing medium when the sprinkler is in an active mode, the holder body comprising an inlet for incoming extinguishing medium, wherein
in the protective position the cover is arranged to protect the release means but, when displaced, is arranged to expose the release means and place the sprinkler in a standby mode in which the release means is intact so as to be able to react to heat and achieve a release of the sprinkler and place it in the active mode, and
the means for achieving the displacement of the cover comprises a device which is displaceable with respect to the sprinkler and which is arranged under fluid pressure to exert a force on a locking means in the cover to make the locking means open and consequently displace the cover to said free position.
The displaceable device preferably comprises a projection area which is arranged to exert a force on the locking means under fluid pressure in a pressure chamber.
The displaceable device preferably comprises a sleeve-like part which together with the holder body defines the pressure chamber, the sleeve-like part comprising the projection area in the area of the pressure chamber. Such a structure is simple and operatively reliable.
The pressure chamber can be in fluid communication via a passage with the inlet when the sprinkler is in the inactive mode. This being the case, an extinguishing medium pressure in the inlet provides said force against the locking device. This provides an extremely simple way for the sprinkler to shift to the standby mode.
Alternatively, the pressure chamber is in fluid communication by means of a pipe, which can be called a control line, such that a fluid pressure in the pipe is arranged to provide said force against the locking device. This embodiment is particularly suitable when the aim is to achieve a sprinkler for a so-called wet pipe system with long pipelines, i.e. a system in which pressurized extinguishing medium is present in the pipelines and at the inlet of the sprinklers when they are in the inactive mode. The control line may have small dimensions and a low pressure compared with the dimensions of and the pressure in the pipelines.
When a sleeve-like part is used, it preferably comprises a cylindrical part which comprises a first cylindrical inner surface and a second cylindrical inner surface in the area of the pressure chamber, the first cylindrical inner surface having a larger diameter than the second cylindrical inner surface so that a shoulder forms between said cylindrical inner surfaces, the shoulder defining said projection area as a ring area. Such a cylindrical part is easy to make and easy to attach to the holder body. Furthermore, in this case the sleeve-like part is preferably sealed against the holder part by a first ring seal positioned in the first cylindrical inner surface and a second ring seal positioned in the second cylindrical inner surface in such a manner that the fluid supplied to the pressure chamber cannot flow out of the pressure chamber. This provides a simple way to hold the sprinkler tight against leakage when in the standby mode.
When a sleeve-like part is used, it is preferably composed of a third cylindrical inner surface arranged to rest tightly against a third ring seal when the sprinkler is displaced to the standby mode. This provides extra sealing against leakage; both the first and third ring seals seal against leakage.
The cover is preferably fluid-tight and hermetically arranged against the sprinkler by means of a seal which is preferably composed of the third ring seal. This provides the sprinkler with effective protection against dirt. The cover preferably comprises a cylindrical groove for the third ring seal, the groove being arranged to exert a compressive force on the ring seal when the cover is in said protective position, so that the ring seal holds the cover in place in said protective position.
The preferred embodiments of the invention are disclosed in the attached claims 2 to 16.
An important advantage of the sprinkler is that it can be heavily exposed to dirt and impurities, i.e. it may be used in applications in which sprinklers have not been considered to operate reliably, and have therefore never been installed. In such applications the sprinkler of the invention is able to operate, typically in response to signals from smoke detectors, without problems. Another important advantage is that it can be placed and used in surroundings in which the release of the sprinkler is to be avoided when it is exposed to heat, typically from hot flue gases, before it is first activated manually or by means of fire detectors in a manner not similar to that involving hot flue gases to place it in the standby mode in which it can then rapidly react to heat. This means that the sprinklers can be used to construct fire extinguishing systems by which extinguishing medium is likely to be discharged only at the site of the fire. The activation of the sprinklers and transition from the inactive to standby mode can be achieved very rapidly in different ways by means of fluid pressure (using different detection systems) without short exposition to heat producing such preactivation. This way no heat is directed to the sprinkler to cause it to shift to the standby mode. The fluid pressure can be produced by means of manual activation which for example starts pumps or opens valves for delivering fluid to the sprinkler, or by means of a fire detector (e.g. smoke, heat detectors which react to surface or radiating heat or optical flame detectors) which gives a signal for activating the fire extinguishing system/sprinkler. The signal can be given to a pump which starts to supply extinguishing medium to the sprinkler, or the detector can be arranged to give a signal to a valve which opens so as to supply fluid (extinguishing medium, for example) to the sprinkler. The structure of the sprinkler of the invention is also very simple; it can advantageously have a conventional glass ampoule as the heat-activated release means and the nozzles can be placed in the usual manner. The sensitive components of the sprinklers, such as the release means, are protected against mechanical impacts which could cause an unnecessary release of the sprinkler.